Currently the number of materials you'd need to stock in your home to be able to print various kinds of products would be quite large (20 or more). That doesn't make sense from an economic perspective.

Let's image, then, that we'll see products made from fewer raw materials because the design changes to accomodate printers. What reason would designers/manufacturers have to do that when they know they won't be able to make a living when their products get pirated?